Exhaust - Boom
Bulletin No. T 86-37File in Group 6F
Number 7
Corp. Ref. No. 806 5661
Date April '86
SUBJECT: EXHAUST BOOM
MODELS AFFECTED: 1985 - 1986 DE VILLES AND FLEETWOODS
Some De Villes and Fleetwoods equipped with an HT4100 engine may experience an exhaust boom (noise) between 1830 - 1890 R.P.M.
To correct this condition, a new exhaust hanger bracket kit (P/N 25527855) has been developed. Vehicles which experience this condition should be serviced using the following procedure:
1. Verify the exhaust boom is present with A/C off.
2. If boom is not present with A/C off, see Serviceman Bulletin 84-102A, Group 1, number 17 and 85-100, Group 1, number 24 for A/C system diagnosis.
FIGURE 1 - NEW EXHAUST HANGER LOCATION:
3. Clamp the new hanger to the tailpipe as shown in Figure 1. The weld-nut on the hanger assembly should line up with the centerline of the muffler.
4. Position the leading edge of the new body mounted exhaust hanger bracket against the old exhaust hanger bracket keeping the bottom edge flush with the bottom of the frame rail. Drill three 5/16 diameter holes in frame using bracket as a guide and secure with the three self-tapping screws included in the kit.
5. Support the exhaust system and remove the original, insulator and attaching bolts. Cut the point from the top bolt to shorten it to 10 mm (13/32 in.) of thread length.
6. Re-install the insulator at the new location.
For warranty purposes, use Labor Operation T6144 at .4 hours.